The number of turns of the coil of a moving coil galvanometer is increased in order to increase current sensitivity by 50%. The percentage change in voltage sensitivity of the galvanometer will be:

Current sensitivity of a galvanometer is given by:

$$ I_s = \frac{nBA}{c} $$

where $$n$$ = number of turns, $$B$$ = magnetic field, $$A$$ = area of coil, $$c$$ = restoring torque per unit twist.

To increase current sensitivity by 50%, we increase $$n$$ by 50%.

Voltage sensitivity is given by:

$$ V_s = \frac{I_s}{R} = \frac{nBA}{cR} $$

When the number of turns increases by 50%, the resistance of the coil also increases by 50% (since resistance is proportional to the length of wire, which is proportional to $$n$$).

New voltage sensitivity:

$$ V_s' = \frac{1.5n \times BA}{c \times 1.5R} = \frac{nBA}{cR} = V_s $$

The voltage sensitivity remains unchanged. The percentage change is 0%.